Docker build log cleaner

Docker build log cleaner for coding agents

Paste Docker BuildKit output and get a compact prompt that keeps the failing layer, package-manager error, Dockerfile context, and exit code.

Docker build logs can bury the one failing command under cached layers, transfer lines, package downloads, progress output, and repeated warnings. tokensift folds that noise while preserving the build evidence a coding agent needs.

Open the main Sift tool View before/after

Before and after

Before: raw paste

$ docker buildx build --progress=plain -t api-image .
#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 1.28kB done
#1 DONE 0.0s
#2 [internal] load metadata for docker.io/library/python:3.12-slim
#2 DONE 0.8s
#3 [1/5] FROM docker.io/library/python:3.12-slim
#3 CACHED
#4 [2/5] WORKDIR /app
#4 CACHED
#5 [3/5] COPY requirements.txt ./
#5 DONE 0.1s
#6 [4/5] RUN pip install --no-cache-dir -r requirements.txt
#6 1.322 Collecting fastapi==0.111.0
#6 1.944 Collecting psycopg2==2.9.9
#6 2.101 ERROR: Could not find a version that satisfies the requirement private-package==0.4.0 (from versions: none)
#6 2.102 ERROR: No matching distribution found for private-package==0.4.0
#6 ERROR: process "/bin/sh -c pip install --no-cache-dir -r requirements.txt" did not complete successfully: exit code: 1

Dockerfile:9
--------------------
   7 | COPY requirements.txt ./
   8 |
   9 | >>> RUN pip install --no-cache-dir -r requirements.txt
  10 | COPY . .
--------------------
ERROR: failed to solve: process "/bin/sh -c pip install --no-cache-dir -r requirements.txt" did not complete successfully: exit code: 1

After: compact debugging brief

Debug Docker build failure.

Type:
- Docker build

Keep:
- cmd: docker buildx build --progress=plain -t api-image .
- base image: python:3.12-slim
- failing step: #6 [4/5] RUN pip install --no-cache-dir -r requirements.txt
- Dockerfile:9 -> RUN pip install --no-cache-dir -r requirements.txt
- error: No matching distribution found for private-package==0.4.0
- exit: process did not complete successfully: exit code: 1

Folded:
- cached layers, dockerfile transfer, package download chatter, repeated solve wrapper lines

Ask: root cause, smallest fix, verify command.

Preserved evidence

  • docker build command
  • base image
  • failing BuildKit step
  • Dockerfile line and command
  • pip package resolution error
  • exit code

Folded noise

  • successful cached layers
  • metadata transfer lines
  • long package download output
  • repeated Docker solve wrapper messages
  • non-root-cause progress output

How to use it well

Paste with --progress=plain when possible. It makes failing step numbers, Dockerfile context, and package-manager errors easier to preserve.

Paste the relevant failure output into the main tool, run Sift, then review the compact brief before sending it to Codex, Claude Code, ChatGPT, OpenCode, or another coding agent.

Privacy note: No LLM API call. No raw logs sent to external model providers, ad providers, or third-party analytics. Hosted submissions may be stored in a private first-party database for diagnostics and retained for up to 30 days by default, so review and redact before use.

Open tokensift and paste your own log.